An Exploration of Nonprehensile Two-Palm Manipulation: Planning and Execution

This paper describes our current research into nonprehensile palm
manipulation. The term ``palm'' refers to the use of the entire device
surface during manipulation, as opposed to use of the fingertips alone. The
term ``nonprehensile'' means that the palms hold the object without wrapping
themselves around it, as distinguished from a force/from closure grasp often
employed by a fingered hand. Indeed, nonprehensile operations such as
purposeful sliding and constrained dropping constitute important palm
primitives.
We have implemented a system for orienting parts using two palms. The system
consists of a planner and an executive. As input, the system expects a
geometric description of a part, its center of mass, the coefficients of
friction between the part and each of the palms, and a start and goal
configuration of the part in stable contact with one of the palms. As output,
the system computes and executes a sequence of palm motions designed to
reorient the part from the specified start to the specified goal
configuration.